A positive correlation between PCNA and the most important histoprognostic factors of cutaneous melanoma has been demonstrated. The aim of our work was to evaluate the efficacy of PCNA in predicting melanoma recurrence and to compare it with that of Breslow thickness. One-hundred and fifteen patients (75 women, 40 men; mean age 50 years) with primary cutaneous melanoma were retrieved. pTNM stages were as follows: stage I, 54 patients; stage II, 31 patients; stage III, 26 patients; and stage IV, four patients. The mean follow-up period was 55 months (range 2-260). Six patients developed lymph node metastases and 28 developed distant metastases; 27 patients died within 2-202 months from diagnosis. Tumour thickness was re-evaluated for each case. PCNA immunostaining was performed using the avidin-biotin complex method and the percentage of PCNA-positive tumour cells was indicated as the PCNA index. In order to evaluate and compare the PCNA index and Breslow thickness as predictors of recurrence, the receiver-operating characteristic (ROC) curve method, based on true-positive and false-positive rates was used. The PCNA index showed the highest true-positive rates and the lowest false-positive rates in the 5-30 interval. The PCNA index optimal cut-off is 20, characterized by 70% sensitivity and 80% specificity; Breslow thickness optimal cut-off is 3.5 mm, with 40% sensitivity and 90% specificity. Our results indicate that the PCNA index has a higher efficacy in predicting locoregional and distant recurrences in patients presenting primary cutaneous melanoma.